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Home , Brian Schmidt, Edwin Hubble, Fritz Zwicky, Jim Peebles, Nicolaus Copernicus

Timeline

Cosmology • 2nd Millennium BCEBC Mesopotamian has a flat,circular enclosed in a cosmic Ocean

• 12th century BCEC Rigveda has some cosmological hymns, most notably the Nasadiya Sukta

• 6th century BCE Anaximander, the first (true) cosmologist ‐ pre‐Socratic philosopher from Miletus, Ionia ‐ Nature ruled by natural laws ‐ Apeiron (boundless, infinite, indefinite), that out of which the originates

• 5th century BCE ‐ Timaeus ‐ dialogue describing the creation of the Universe, ‐ demiurg created the world on the basis of geometric forms (Platonic solids)

• 4th century BCE ‐ proposes an Earth‐centered universe in which the Earth is stationary and the , is finite in extent but infinite in time

• 3rd century BCE ‐ proposes a heliocentric (‐centered) Universe, based on his conclusion/determination that the Sun is much larger than Earth ‐ further support in BCE by Seleucus of Seleucia

• 3rd century BCE ‐ book : diameter of cosmos ~ 2 lightyears ‐ heliocentric Universe not possible

• 3rd century BCE Apollonius of Perga ‐ epicycle theory for lunar and planetary

• 2nd century CE Ptolemaeus ‐ /Syntaxis: culmination of ancient Graeco‐Roman ‐ Earth‐centered Universe, with Sun, and revolving on epicyclic around Earth

• 5th‐13th century CE Aryabhata (India) and Al‐Sijzi (Iran) propose that the Earth rotates around its axis. First empirical evidence for Earth’s rotation by Nasir al‐Din al‐Tusi.

• 8th century CE Puranic Hindu cosmology, in which the Universe goes through repeated cycles of creation, destruction and rebirth, with each cycle lasting 4.32 billion years. •

• 1543 ‐ publishes heliocentric universe in De Revolutionibus Orbium Coelestium ‐ implicit introduction : Earth/Sun is not special

• 1609‐1632 ‐ by means of (telescopic) observations, proves the validity of the heliocentric Universe.

• 1609/1619 ‐ the 3 Kepler laws, describing the elliptical orbits of the planets around the Sun

• 1687 ‐ discovers Gravitational Force as agent behind cosmic motions ‐ publishes his Principia (Philosophiae Naturalis Principia Mathematica), which establishes the natural laws of and (the latter only to be replaced by Einstein’s theory of GR)

• 1755 ‐ asserts that nebulae are really separate from and outside from the , ‐ calling these Island

• 1785 ‐ proposes theory that our Sun is at or near the center of ou (Milky Way)

• 1826 Heinrich Wilhelm Olbers ‐ Olber’s paradox (why is the night sky dark ?)

• 1837 Friedrich Bessel, Thomas Henderson, Otto Struve ‐ measurement of a few nearby : the first measurement of any distances outside the . ‐ establishes the vast distances between the stars

• 1848 Edgar Allan Poe ‐ first correct solution to Olber’s paradox in Eureka: A Prose Poem, an essay that also suggests the expansion of the universe

• 1860 William Huggins ‐ develops astronomical spectroscopy : Orion is mostly made of gas, the Andromeda nebula dominated by stars

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• 1905 ‐ Special ‐ and time are not separate continua, instead they define a 4‐dim. continuum

• 1915 Albert Einstein ‐ General Theory of Relativity: ‐ represents an entirely new theory of gravity, in which gravity is the result of the local curvature of space, hence replacing the action‐at‐a‐distance theory of Newton. ‐ spacetime becomes a flexible dynamic medium, warped by energy density

• 1917 ‐ first general relativistic cosmology, ‐ empty expanding Universe with

• 1912 Henrietta Leavitt ‐ stars period‐ relation ‐ crucial step in measuring distances to other galaxies

• 1920‐1921 & Heber Curtis ‐ Shapley –Curtis debate or “”, National of ‐ debate on the distances to spiral nebulae: are they individual galaxies like the Milky Way or are they part of the Milky Way

• 1923 ‐ measures distance to few nearby spiral nebulae (, , NGC 6822) ‐ distances place them far outside our Milky Way ‐ demonstrates that the spiral nebulae are galaxies outside our own Galaxy, the Milky Way ‐ In other words, the Galaxy loses its central unique position and the Universe turns out to be much, much larger

• 1922 ‐ finds that spiral nebulae are systematically redshifted, ie. moving away from us

• 1922 ‐ Friedmann solution to the Einstein field equations, now known as Friedmann‐Robertson‐Walker‐Lemaitre equations ‐ solutions for a perfectly uniform space ‐ imply expansion of the space

• 1927 Georges Lemaitre ‐ solutions for Einstein field equations, for a perfectly uniform space, confirming Friedmann ‐ discusses the implications, that of an expanding Universe and the creation of the Universe ‐ predicts distance‐ relation (later known as Hubble relation) ‐ may indeed have discovered the expansion of the Universe from existing data (ongoing discusssion)

• 1929 Edwin Hubble ‐ discovery linear redshift‐distance relation (the Hubble relation) ‐ ie. the discovery of the EXPANDING UNIVERSE

• 1933 Edward Milne ‐ formulation of the ‐ Universe is Isotropic and Homogeneous (on scales larger than 100 million lightyears)

• 1933 ‐ discovery of existence of , from galaxy velocities in of galaxies

• 1934 Georges Lemaitre ‐ Cosmological constant (free factor in Einstein field equations): interpretation in terms of vacuum energy with an unusual perfect equation of state

• 1946 Evgeni M. Lifschitz ‐ formulation, in a relativistic context, of gravitational instability in an expanding universe, the prevailing theory for the formation of structure in the Universe

• 1946 ‐ Hot ‐ predicts the existence of a cosmic radiation field with a temperature of 50 K (is 2.725K), presuming all chemical elements were formed in the hot Big Bang.

• 1948 Ralph Alpher , , George Gamow ‐ the a‐b‐g paper ‐ describes how the Big bang would by means of nuclear synthesis in the early universe create hydrogen, helium and heavier elements

• 1948 Ralph Alpher & ‐ as a consequence of their studies of nucleosynthesis in the early expanding Big Bang universe, theoretical prediction of the existence of a residual, homogeneous, isotropic blackbody radiation ‐ they estimate "the temperature in the universe" at 5K. ‐ in 1965 discovered as the Cosmic Microwave Background Radiation

• 1948 , , ‐ proposal Steady State Cosmology, based on the perfect cosmological principle

• 1950 Fred Hoyle ‐ the term Big Bang, meant in a derisive way

• 1957 Margaret Burbidge, Geoffrey Burbidge, William Fowler & Fred Hoyle ‐ landmark B2FH paper ‐ Synthesis of the Elements in Stars ‐ describes how all elements, heaver than lithium, are synthesize by nuclear processes in the cores of stars ‐ We are stardust ! Edwin Hubble (1889‐1953)

v = H r Hubble Expansion • 1963 Maarten Schmidt ‐ discovery of the first quasar, active nuclei of galaxies visible out to very high in the Universe

• 1965 Arno Penzias & Robert Wilson ‐ Discovery of the 2.7K Microwave Background Radiation (CMB) ‐ ultimate of the Hot Big Bang ‐ Nobelprize in 1978

• 1965 Robert Dicke, , Peter Roll & David Wilkinson ‐ interpretation of the CMB as the relic radiation from the Big Bang

• 1966 Jim Peebles ‐ predicts the correct helium abundance, produced as a result of early Universe

• 1966 & George Ellis ‐ Singularity Theorem ‐ they show that any plausible general relativistic cosmology is singular 1965: Penzias & Wilson

discovery Cosmic Microwave Background Radiation Echo of the Big Bang • 1970 ‐ Zeldovich formalism ‐ theory of anisotropic gravitational collapse for the formation of structure in the Universe

• 1980 , Alexei Starobinsky ‐ Inflationary Big Bang universe ‐ possible solution to the socalled horizon and flatness problems of standard Big Bang models ‐ has become a key element of the standard Big Bang model

• 1982‐1984 Jim Peebles, Dick Bond, George Blumenthal ‐ universe dominated by

• 1983‐1987 Klypin & Shandarin 1983 Davis, Efstathiou, Frenk & White 1985‐1987 ‐ the first large computer simulations of cosmic ‐ DEFW show that cold dark matter based simulations produce a reasonable match to observations

• 1986 de Lapparent, Geller & Huchra discovery of the Cosmic Web by the CfA2 survey “Slice of the Universe” ‐ final confirmation of earlier suggestions/indictions of a weblike/cellular structure in the Universe ‐ by Einasto et al. (1980) while ‐ later the reality of the Cosmic Web got confirmed in an unambiguous fashion by the maps of the 2dFGRS redshift survey (1997‐2002)

• 1990 George Efstathiou, Steve Maddox & Will Sutherland ‐ APM survey: computer processed measurement of the galaxy distribution on the southern sky ‐ first direct detection and claim of the impact of a Cosmological Constant

• 1990 COBE CMB satellite, John Mather ‐ precise measurement of the blackbody spectrum of the Cosmic Microwave Background ‐ confirmation of blackbody nature of CMB, to a precision of 1 in 105, the strongest and ultimate evidence for the reality of the Hot Big Bang ‐ T=2.725 K ‐ Nobelprize physics 2006

• 1990 COBE CMB satellite, ‐ discovery of tiny anisotropies in the CMB, ‐ the seeds of structure formation in the Universe ‐ confirmation of the gravitational instability theory for structure formation in the Universe ‐ provides the baby picture of structure of the Universe “only” 379,000 years after the Big Bang ‐ Nobelprize physics 2006

• 1997‐2002 2dFGRS galaxy redshift survey ‐ first large scale systematic survey of the spatial galaxy distribution ‐ conducted with the 3.9m Anglo‐Australian Telescope ‐ mapped the positions of 232,155 galaxies in 2 narrow slices out to a redshift of 0.2 ‐ structure mapped is that of a Cosmic Web

• 1998 Cosmology Project, High‐Z Supernova Search Team, lead by , & ‐ discovery of the acceleration of cosmic expansion ‐ provides first direct evidence for the existence of a non‐zero cosmological constant ‐ Nobelprize Physics 2012

• 2000‐ (SDSS) Maj‐‐ multi‐filter imaging and spectroscopic redshift survey using a dedicated 2.5‐m wide‐angle optical telescope at Apache Point Observatory in New Mexico ‐ systematic mapping of the spatial galaxy distribution in major regions of the nearby Universe ‐ as yet around 2,000,000 galaxies ‐ clustering consistent with the cold dark matter theory of cosmic structure formation, including Cosmological Constant, the socalled LCDM cosmology - Universe 380.000 yrs after Big Bang Precision - 13.8 Gyrs ago (13.798±0.037 Gyrs) - Temperature T = 2.72548±0.00057 K Cosmology - temperature/density fluctuations (DT/T<10-5)

Planck satellite map of the primordial Universe • 2000 Witman et al., Bacon et al., Kaiser et al., van Waerbeke et al. (4 independent groups) discovery/detection Cosmic Shear ‐ gravitational lensing by cosmic distribution ‐ induced by the dominant dark matter component in the cosmic mass distribution ‐ proviedes a new and competitive probe of cosmological parameters

• 2003 WMAP CMB satellite ‐ Wilkinson Microwave Anisotropy Probe, ‐ US satellite mission measuring the CMB to subhorizon scales ‐ mapping of cosmic acoustic waves and measurement angular fluctuation spectrum ‐ opening era of Precision Cosmology ‐ establishes accurate age determination of the Universe: 13.7 Gyr ‐ establishes that the Universe has zero curvature (flat Universe) ‐ established reality of Cosmological Constant/

• 2005 Cole et al. , Eisenstein et al. discovery Baryonic Acoustic Oscillations ‐ from the maps of galaxy distribution from the 2dFGRS and SDSS galaxy redshift surveys, the first detection of the remnant acoustic oscillations: remnant of the primordial sound waves ‐ new probe that confirms realiyt of Dark Energy/Cosmological Constant

• 2013‐2015 CMB satellite ‐ European satellite mission measuring the CMB to unprecedented detail and accuracy ‐ maps the polarization of the cosmic microwave background ‐ detects the gravitational lensing of the CMB ‐ establishes the to 13.8 Gyr